The known slide fasteners of this type (German Offenlegungsschrift DE-OS 25 37 059) include a new generation of slide fasteners which in various embodiments are known as so called ladder rung zippers. In all these slide fasteners the closure members form a semifinished article with planar elements as ladder rungs and textile spars after the injection molding process and after the removal from the form wheel or from the assembly of form wheel and form band. The initially planar elements or fastening members are formed into the coupling elements by U-shaped bending. Upon the U-shaped bending the coupling head proper is generated, even though coupling surfaces of the coupling head can be formed during the injection molding process. By way of the U-shaped bending an eye also is generated in the region of the coupling head. The coupling head of the other slide fastener half with its coupling surfaces in each case is complementary to and fits into the eye. The eye generated upon bending of the initially planar rungs is essential for the coupling process. This may be the reason that slide fasteners of this type and similar ones are known only with U-shaped fastener members whether the U-arms of the fastener members are welded together or not.
The known slide fasteners of this type have proven successful in various embodiments in general. Nevertheless there are deficiencies. By injection molding extremely fine fastener members cannot be produced because the fastener members themselves must be thick orthogonal to the closure plane based on the U-shape of these fastener members. In addition the reforming of the initially planar rungs of the semifinished material to U-shaped fastener members represents additional work which has to be performed with very high precision. This is the case especially when the arms of the fastener members are welded together. While the described continuous injection molding process with form wheel and form band allows very high production speeds, the velocity of reshaping the initially planar rungs of the semifinished material to the U-shaped fastener members is substantially less. This interferes with the work speed and the economic performance of a complete production line. If the bending is not performed with the precision required then variations occur which interfere with the quality and in particular with the break-up strength. This is the case especially when fine soide fasteners are to be made as are required in the textile industry.